Press die assembly for bending machines



Feb. 14, 1967 H. SCHMIDT 3,303,683

PRESS DIE ASSEMBLY FOR BENDING MACHINES Filed NOV. 27, 1963 2 Sheets-Sheet l I NVENTOR.

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PRESS DIE ASSEMBLY FOR BENDING MACHINES Filed Nov. 27, 1963 2 Sheets-Sheet 2 lac 1am flttorne United States Patent 3,303,683 PRESS DIE ASSEMBLY FOR BENDING MACHINES Hans Schmidt, Aurora, 111., assignor to Pines Engineering Co., Inc., Aurora, 111., a corporation of Illinois Filed Nov. 27, 1963, Ser. No. 326,543 Claims. (Cl. 72-154) The invention relates to improvements in apparatus for bending tubular stock and like products and is particularly concerned with the novel construction and assembly of the press die assembly thereof.

Horizontal tube bending machines comprise an elongated base or frame structure that terminates at one end in a nose portion carrying a rotatable bending die with which is associated a movable wiper die disposed to wrap the lead end of a length of tubular stock around the bending die for performing a bend in the tubular stock. The trailing portion of the length of tubular stock entering the bending die is held firmly between a back-up die or block and a press die, the latter being movable away from the back-up block to permit feeding of the stock to the bending die. The present invention is concerned with the construction of the press die mounting structure which embodies a novel master bar assembly that is adapted to be shifted, while the press die is in pressing position, so as to resist stretching and expansion of the tubular stock during the bending operation.

More specifically, during a bending operation, the tubular stock tends to stretch should its trailing end be held rigidly. This stretching causes the wall thickness of the tubular stock to be reduced. The present press die assembly includes power means in the form of a hydraulic motor that operates to urge the press die in the direction of stretch so as to prevent such stretching and thus maintain the desired wall thickness. When pressure of the press die is relieved at the end of a bending operation, the motor is reversed to return the press die to its initial or start position for repeat operation.

It is, therefore, and object of the invention to provide a novel press die assembly.

Another object is to provide a press die assembly for tubular stock bending machines, with novel means to advance the press die, while in pressuring position, in the direction of stretch of the tubular stock.

Another object is to provide a novel mounting for a press die.

Another object is to provide, in a bending apparatus, a ruggedly constructed press die assembly which is not expensive to manufacture, and is very eflicient in use.

The structure by means of which the above noted and other advantages and objects of the invention are attained will be described in the following specification, taken in conjunction with the accompanying drawings, showing a preferred illustrative embodiment of the invention, in which:

FIG. 1 is a plan view of one end of a tube bending machine, showing the novel press die assembly in advanced position assumed during a bending operation;

FIG. 2 is an enlarged elevational view of the press die assembly, showing parts of the master bar broken away;

FIG. 3 is an end elevational view of the press die assembly, as viewed in the direction of arrows 33 of FIG. 1; and,

FIG. 4 is an elevational view of the other end of the press die assembly.

Referring to the exemplary disclosure in the accompanying drawings, and particularly to FIG. 1 thereof, the bending apparatus includes an elongated housing 11 having a nose 12 at one end in which is journalled, on a vertical axis, a bending die 13. The bending die and its mounting is of usual construction and said die has a 3,303,683 Patented Feb. 14, 1967 peripheral groove 14 in which the lead end of a length of tubular stock 15 to be bent is adapted to seat. Also mounted firmly on the upper surface of the housing is a back-up block 16 having a groove 17 in one face thereof to receive the trailing portion of said tubular stock.

In operation, insofar as described, the length of tubular stock 15 is arranged over the top of the machine in such manner as to lie within grooves 14 and 17. A press die 18, forming part of an assembly to be described in detail presently, then is moved toward the back-up block 16 into tight abutment with the tubular stock so as to hold the stock firmly during the subsequent bending operation. Bending of the tubular stock about bending die 13 is effected by means of a conventional wiper die 19 carried on a radial arm 21 that is pivotally mounted on the axis of the bending die, and which arm is rotated about its axis a distance necessary to perform the desired bend in the tubular stock. This bending is illustrated in FIG. 1.

Bending by conventional machines, wherein the press die is immovable in any direction except toward and away from the tubular stock, results in stretching of the stock and consequent thinning out of the walls thereof. In the present construction means is provided, in association with the press die assembly, to prevent such stretching and wall thinning. This means functions to positively drive the press die 18 in the direction of stretch thus advancing the clamped tubular stock toward the bending die to compensate for any tendency of the tubular stock to stretch during the bending operation.

As best shown in FIG. 1, the press die 18 is carried firmly on a master bar 22 that is slidably mounted in a base 23 mounted on the apparatus frame 11 in the region of the back-up block 16. More particularly, the master bar is of considerable length and, as best shown in FIGS. 3 and 4, it is substantially H-shaped in section. It includes a front wall 24, a back Wall 25 of lesser height, and a connecting web 26. The front wall has the press die secured firmly to it as by means of brackets 27 that are secured to the press die by means of bolts 28 and spacers 29, and which have hook-like end portions that engage over the top margin of front wall 24 for supporting the press die in a fixed position thereon. Screws 31 secure the brackets 27 to the master bar, thus locking the press die firmly to the master bar.

The master bar 22 is longitudinally slidable in a base structure which comprises a horizontally disposed U- shaped casting 32 having a pair of rollers 33 journalled between its legs on vertical axes 34, and against which the rear surface of the master bar back wall 25 bears at all times. The free edge of the lower leg of said base 32 mounts a pair of longitudinally spaced apart rollers 35 upon which the bottom edge of said back wall rides. The

upper leg of said base carries a pair of longitudinally spaced upstanding ears 36 which overhang the master bar back wall 25 and carry, firmly suspended from each, a block 37 each having a lateral roller 38 thereon that rides upon the upper edge of the master bar black wall, and a bottom roller 39 that engages and rides along the inside surface of said back wall 25. In this manner the master bar 22 is held to the base and is freely slidable longitudinally relative thereto.

A rack 41 is secured firmly to the bottom surface of the master bar web 26 and extends therealong for a considerable portion of its length.

The base 32 is slidable laterally on the frame 11 so as to carry the press die 18 toward and away from the back up block 16 for clamping and releasing the tubular stock therebetween. Preferably, the base is connected to a ram 42 having a piston on one end operating in a hydraulic cylinder 43 which functions in response to the presence or absence of hydraulic pressure in the cylinder for moving the base.

In operation, when a length of tubular stock 15 is positioned for bending, the press die 18 and its master bar 22 are advanced laterally to carry the press die into clamping engagement therewith, with the lead end of the press die and master bar in alignment with the axis of the bending die, as shown in FIG. 1. As the bending operation progresses, the tubular stock tends to stretch and thus would cause a diminishing in the thickness of its wall were the tubular stock held rigidly. The present construction afiords means to urge the tubular stock axially toward the bending die during the bending operation thus preventing any undue stretching thereof. This axial movement of the tubular stock is slight because were it excessive the stock would become malformed at the point of bending. This movement is best controlled by providing power means to urge the master bar and press die thereon in the direction of stretch and to return it after the bending operation is completed and the press die relieved of pressure.

The power means provided for advancing and retracting the master bar 22 in a longitudinal direction preferably comprises a vane type hydraulic motor 44. This type of motor is used because its output shaft rotation can be to maximum r.p.m., in either direction under load. The motor is mounted on an L-bracket 45 secured to one end of the base 32, as by bolts 46, and its shaft 47 carries a gear 48 that meshes at all times with the rack 41. During a bending operation, the motor is operated in a direction to urge the tightly clamped press die and its master bar in the direction of stretch. However, because of the tight clamping of the tubular stock between the press die and the fixed back-up block 16, movement of the press die is restrained. It functions sufiiciently to push or urge the tubular stock in the direction of the bending die commensurate with the tendency of the stock to stretch, consequently any tendency to stretch is compensated for by positive advance of the clamped portion of the tubular stock toward the bending die. This prevents the tubular stock from being stretched hence there is no thinning out of the walls thereof. As soon as the bending operation is completed, means (not shown) functions to relieve the press die and reverse the operation of the motor 44 for returning the press die to its initial start position longitudinally.

Although I have described a preferred embodiment of my invention, in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as many details of the structure disclosed may be modified or changed without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact construction described.

What I claim and desire to secure by Letters Patent of the United States is:

1. In apparatus for bending tubular stock, a bending die and a wiper die associated therewith, a back-up block for the trailing end of the tubular stock, a press die movable into tight clamping engagement with the tubular stock in opposition to the back-up block, and means operable to advance the press die in the direction of the bending die during a bending operation.

2. The apparatus recited in claim 1, in which the means to advance the press die comprises a hydraulic motor.

3. The apparatus recited in claim 1, in which the means to advance the press die comprises a reversible hydraulic motor.

4. The apparatus recited in claim 1, in which the means to advance the press die comprises a master bar upon which the press die is mounted firmly, and a hydraulic motor to move the master bar.

5. In apparatus for bending tubular stock, a bending die, a wiper die operably associated with the bending die for bending a piece of tubular stock around the bending die, and means to clamp the tubular stock in position to be engaged by the wiper die, said means comprising a back-up block and a press die between which the tubular stock is clamped, and means operable to urge the press die in the direction of the bending die during a bending operation.

6. In a bending machine, a press die assembly comprising a base structure, a master bar slidable in said base structure, a press die mounted firmly on said master bar, and power means to shift the master bar and press die in unison in a longitudinal direction.

7. The bending machine recited in claim 6, in which a rack is mounted on the master bar and power operated gear means is engaged with said rack.

8. In a bending machine, a press die assembly comprising a back-up block, a base structure slidable toward and away from said back-up block, a master bar mounted on said base structure, and a press die carried by said master bar for clamping a workpiece against the back-up block, said master bar and attached press die being movable as a unit longitudinally relative to the base and backup block.

9. The bending machine recited in claim 8, in which the base structure carries anti-friction rollers upon which the master bar rides.

10. In a bending machine, a bending die, a wiper die operably associated with the bending die for bending tubular stock around the bending die, a stationary backup block for the trailing end of the tubular stock, a movable base structure, a master bar slidable 1ongitudinally in said base structure, a press die mounted firmly on said master bar, means operable to move the base structure toward the back-up block for clamping the tubular stock between the back-up block and the press die, and means operable to move the press die and master bar as a unit longitudinally relative to the back-up block and toward the bending die during a bending operation.

References Cited by the Examiner UNITED STATES PATENTS 3,242,710 3/1966 Hamlin 72156 CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Assistant Examiner. 

1. IN APPARATUS FOR BENDING TUBULAR STOCK, A BENDING DIE AND A WIPER DIE ASSOCIATED THEREWITH, A BACK-UP BLOCK FOR THE TRAILING END OF THE TUBULAR STOCK, A PRESS DIE MOVABLE INTO TIGHT CLAMPING ENGAGEMENT WITH THE TUBULAR STOCK IN OPPOSITION TO THE BACK-UP BLOCK, AND MEANS OPERABLE TO ADVANCE THE PRESS DIE IN THE DIRECTION OF THE BENDING DIE DURING A BENDING OPERATION. 